Exploring soil nutrient additions: Evaluating effects of long-term fertilization on low-Arctic tundra microbiomes and assessment of nano-phosphate fertilizer on soybean (Glycine max)
Out of necessity, plant nutrient requirements must be locally met, which explains the importance of soil fertility and soil microbial community structure. It is thus vital to understand the impact of climate change and technological breakthroughs on the microbes associated with natural vegetation and our crops. This thesis attempts to address these questions with two distinct investigations. In the first investigation, soil communities were examined in long-term maintained fertilizer and warming treatments in the Arctic tundra. The microbiomes associated with Arctic birch (Betula glandulosa) within the 5 treatment plots (control, high nitrogen (N), high phosphate (P), high N+P, and warming) near Daring Lake, NWT were sampled. Microbiome analysis of bacterial and fungal communities, using 16s rRNA and ITS (Internal Transcribed Spacer) analysis respectively, showed differences in bacterial communities with an increase in the family Xanthomonadaceae present in the N plus P treatment, while control and warming treatments showed similar soil and rhizosphere microbiome structures. There was an increase in Thelephora fungi in the high P treatment. In the second chapter, microbial communities and plant growth were monitored after treatment with nano-phosphate fertilizer. Nano-hydroxyapatite (nHA) has been cited as more environmentally friendly and efficient than traditional fertilization with inorganic phosphate (P2O5). The needle-like nHA was used to evaluate the impact on early microbiome establishment in soybean (Glycine max) and in the soil, in an agriculturally realistic manner, utilizing 16s rRNA gene sequencing. Little difference was found in the soil structure and rhizosphere microbiomes between controls and nHA treatments. Growth experiments implementing nHA at agricultural recommended levels of P2O5, added to soil at the time of planting, did not show a significant increase in growth, biomass, or yield compared with P-deprived controls, suggesting that the nHA used here did not function as an effective fertilizer. The effectiveness of nano-fertilizers is likely influenced by their physicochemical properties (i.e. shape and surface) and their interactions with the soil matrix, making it important to evaluate these factors when designing new nano-phosphate fertilizers. Traditional P fertilization as used in the Daring Lake plots, was more effective, with a higher impact on the associated microbial community structure.
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